I. Principle of operation.

　　The complex bed is a system in which water passes sequentially through a cation bed with hydrogen-type cation exchange resin and an anion bed with hydrogen-oxygen-type anion exchange resin. The hydrogen type cation exchange bed is used to remove the cations in the water; the hydroxide type anion exchange bed is used to remove the anions in the water. Various mineral salts in the water can be largely removed by the complex bed. In order to obtain a better effect of salt removal, the cation bed is loaded with strong acid cation exchange resin, and the anion bed is generally loaded with strong alkali anion exchange resin.

2, the scope of application.

Compound bed is generally placed after the electrodialysis device or reverse osmosis device (or directly applied to water with low salt content), the water can be further desalinated to produce higher purity water, widely used in electronics, chemical, pharmaceutical, atomic energy, electric power and other industries.

3, the equipment composition and performance.

Compound bed shell production materials are glass fiber reinforced plastic, organic glass, stainless steel, carbon steel, anti-corrosion, etc., appearance for the garden column type, diameter Ø200-2500mm, water production from 0.5t / h a 98t / h. Yang bed loaded with strong acid cation exchange resin, anion bed loaded with strong alkali anion exchange resin, loading height is generally in lO00 - 2400mm, small There is no support layer at the bottom of the filter cap type equipment, there is a multi-level quartz sand support layer at the bottom of medium and large equipment with different particle sizes, and there is a 200mm thick quartz sand pressure grease layer at the top layer of the resin in the countercurrent regeneration fixed bed. Plexiglass column operating pressure ≤ 0.15MPa, other materials of the equipment operating pressure ≤ 0.6MPa. Yang bed equipped with acid tank, acid pump regeneration system, negative bed equipped with alkali tank, alkali pump regeneration system.

4, the new equipment before the operation of the preparatory work.

1、Grading of medium and large equipment support layer (except for small equipment of plexiglass)

The thickness and gradation of quartz sand support layer

Note: Ø1600, Ø2500 refers to the diameter of the equipment.

2、Filling of resin.

(1) Thoroughly clean and wash all parts of the ion exchanger.

(2) small exchanger without support layer, add a certain height of water before loading resin to avoid resin impact on the bottom of the exchanger

(3) support layer of quartz sand to be thoroughly rinsed clean.

(4) Resin filling height is 2/3 of the effective height of the column for small and medium-sized ones, and for large ones, according to the actual situation such as water quality and quantity.

Determine the filling height and close the exchanger after meeting the requirements. Backwash and settle the resin, open the exchanger after draining, remove the fine particles of resin or soft balls floating on top of the resin layer, and fill the resin if the height of the resin layer does not meet the requirements.

V. Regeneration of resin.

(a) Regeneration of strong acidic cation exchange resin in cation bed.  

1. Yang bed backwashing: Open the main inlet valve (the main valve).

Open the total water inlet valve (7), regulating valve (11), backwash valve (12), the water enters from the bottom of the equipment, the upper discharge valve (14), the resin evenly relaxed and expanded, after which the water flow rate can be increased to wash out the principle of resin, wash until the water is clear. Finally, discharge from the lower discharge valve (13).

2、Regeneration agent preparation.

The regeneration agent is prepared with chemically pure hydrochloric acid and water of high purity to form a regeneration solution with a concentration of 5%. The amount used is about 2 times the volume of the resin.

3, downstream regeneration, the configuration of the regenerant with acid pump through the acid valve (9), water valve (10) into the column, the flow rate is generally controlled at 4-8m / h, the pressure should not be too large, the liquid level is maintained at lOOmm above the resin level, soak 1.5-2 hours to open the lower discharge valve (13) to drain the column acid.

4, counter-current regeneration: open the upper discharge valve (14), regeneration liquid from the acid pump through the acid valve (9), regulating valve (5), backwash valve (12) into the column, regeneration liquid flow rate of 1.6-2m / h, time 40-60 minutes, soak 1.5 ~ 2 hours, from the lower discharge valve (13) to drain the column of acid.

5, dynamic regeneration, according to the downstream regeneration procedure, the flow rate must be slow, rinse the resin for 15-30 minutes until the regeneration solution is used up.

6, positive washing: use the previous level of produced water (fresh water produced by electrodialysis, fresh water produced by reverse osmosis) to rinse the resin from the upper part of the equipment through the total water inlet valve (7) and water inlet valve (10). The flow rate must be uniform, detect the PH value of the water from the lower discharge valve (13) to 5-6 and stop flushing. 

7、Running: Open the total water inlet valve (7), water inlet valve (10) and water outlet valve (12) to supply water to the cathodic bed.

(II) regeneration of strong alkaline anion exchange resin in the anion bed  

1. Backwashing of the anion bed.

　　Open the total water inlet valve (7), regulating valve (11, 16), cathodic bed backwash valve (17) water from the bottom of the equipment, the upper discharge valve (19) discharge, resin uniformly relaxed expansion, after which the water flow rate can be increased to wash out the principle of resin, wash until the water is clear.

2、Regeneration agent preparation.
The regeneration agent is a regeneration solution with a concentration of 5% made of chemically pure sodium hydroxide and pure water. The amount used is about 2 times the volume of the resin.

3, downstream regeneration, the configured regenerant with alkali pump through the alkali valve (8), regulating valve (11), cathodic bed into the water valve (15) into the column, the flow rate is generally controlled at 4-8m / h, the pressure should not be too large, the liquid level is maintained at 10cm above the resin level, soak 1.5-2 hours, open the lower discharge valve (18) to drain the column of alkali.

4, counter-current regeneration: open the upper discharge valve (19), regeneration liquid with alkali pump through the alkali valve (8), regulating valve (11, l6), negative bed recoil valve (17) into the column, regeneration liquid flow rate l.6-2m / h, time 40-60 minutes, soak 1.5-2 hours, drain the column from the lower discharge valve (18) acid.

5, dynamic regeneration, valve operation according to the downstream regeneration procedure, the flow rate must be slow, rinse resin l5-30 minutes, until the regeneration solution is used up.

6, positive washing: use the previous level of produced water (fresh water produced by electrodialysis, fresh water produced by reverse osmosis) to rinse the resin from the upper part of the equipment through the total water inlet valve (7), regulating valve (11), and cathodic bed water inlet valve (15). The flow rate must be uniform, and the PH value of the discharge water from the lower discharge valve (18) is detected to reach 8-9 to stop flushing.

7、Running: The produced water from Yang bed enters Yin bed through Yin bed inlet valve (15) and supplies water to the next level equipment through Yin bed outlet valve (17).

Caution.

① just after the regeneration of ion exchange column needs to flush for ten minutes, just flush when the water quality is poor, need to wait until the water qualified, can be put into normal operation.

② ion exchange column into the water must first open the exhaust valve, wait until the column is completely filled with water, and then close it.  

③ new column water if not qualified, should immediately stop the water stop a few hours before running, the water quality will be greatly improved.  

④When the incoming water temperature in winter is low anion exchange resin regeneration, the alkali solution should be warmed to more than 20 ℃.

⑤ Never backwash with high speed and high flow rate before each regeneration, when the cation bed is regenerated after 10-20 cycles, a high speed and high flow rate backwash can be carried out.

⑥When backwashing, pay attention to whether the resin rises slowly; when the resin lump rises and does not disperse for a long time, the water inlet valve should be closed immediately and the drain valve should be opened to wait for the resin to flip and loosen before backwashing again; after backwashing, the water in the column should not be emptied, and the water cushion layer of 20cm is generally kept on the top surface of the resin; otherwise, when the regeneration liquid flows in, a large number of bubbles will be generated, which will affect the regeneration effect.

Diagram of Yang-bed and Yin-bed pipe valves

Valve summary list

I. Mixing bed operation principle.

　　Ion exchange mixed bed is in an exchanger, according to a certain proportion of both strong acid cation exchange resin, but also strong alkali anion exchange resin, in the case of mixing uniformly, the primary desalinated water (electrodialysis or reverse osmosis or complex bed water) through the downstream, and get a higher pure water. This method is more advanced, equivalent to tens of thousands of compound beds in the work, so the quality of the pure water produced is very high, is the best way to prepare pure water and high purity water.

Second, the resin filling situation:

Mixed bed filled with anion and cation exchange resin volume ratio of 2:1. in the lower part of the ion exchanger there is an acid discharge pipe for cation resin regeneration into the acid, control the interface of the acid does not exceed the interface of the cation resin.

Mixed bed exchanger filled with resin total height: small and medium-sized about 2 / 3 of the effective height of the exchanger; large according to the actual situation of water quality, water and so on.

Third, the mixed bed operation operation:

Generally divided into backwashing, stratification, negative resin regeneration, positive washing, positive resin regeneration, flushing, mixing and positive washing and other eight steps. 

1、Backwashing.
Water from the bottom into, on the exhaust port discharge, resin uniformly loose expansion, can increase the water flow rate, in order to wash out the principle of resin, wash until the water is clear.    The
Valve operation: open the inlet valve, regulating valve, backwash valve, outlet valve and exhaust valve.

2. Stratification.
Use the specific gravity difference between Yin and Yang resin (Yang resin specific gravity is l.23-1.28, Yin resin specific gravity is 1.06-1.11) to stratify by backwashing; backwashing stratification flow rate is about 10m/h (backwashing can also discharge some impurities and foreign matter to ensure the next cycle is normal) after backwashing to loosen the resin in the column, turn off the water source and let the resin in the column fall slowly, the specific gravity of Yang resin will If the stratification is not satisfactory, the above steps can be repeated until the yin and yang resins are completely separated.

Caution.

①The backwash must be thorough, and must achieve complete loosening of the resin in the mixed bed (the operation must make the resin have sufficient expansion height).
②The resin must settle slowly in the column.
③ stratification results must be completely adequate (do not make a dead corner near the lower cloth water).   

3、Regeneration of anion exchange resin.
(1) regenerant preparation: regenerant is the concentration of 5% NaOH solution, the dosage is 2-3 times the volume of the anion resin.
(2) regenerant use: the prepared regenerant will be pumped into the column (note that the pressure should not be too high), the liquid level is maintained at about 10cm above the resin level, soak for 1.5-2 hours, drain the column of waste lye.
Valve operation: open lye inlet pump valve, lye pump pressure reducing valve, lye inlet valve, mixed bed inlet valve, exhaust valve (where the lye pump pressure reducing valve is to adjust the pressure of inlet lye; open the lower discharge valve when discharging).

(3) Dynamic regeneration: pump the remaining regeneration solution into the column, the flow rate (3-5m / h) must be slow, flush the resin, 15-30 minutes, until the regeneration solution is used up.
Valve operation: open the alkali into the pump valve, alkali pump pressure reducing valve, mixed bed into the alkali valve, mixed bed into the water valve, exhaust valve, emission valve (where the alkali pump pressure reducing valve to adjust the pressure of the incoming alkali).

4, positive washing: flush resin from the top with primary desalinated water, the flow rate (10-15m / h) must be uniform, test the bottom of the ion exchange column water with PH test paper, PH value of 8-9, you can stop flushing.
Valve operation: open the water inlet valve, mixed bed water inlet valve, exhaust valve, discharge valve.   

5, cation exchange resin regeneration.

(1)Preparation of regenerant: regenerant is HCL solution of 5% concentration, the dosage is 2-3 times of the volume of cation resin.   
(2) regenerant use: the prepared regenerant will be pumped into the column (note that the pressure should not be too large) the liquid level is maintained in the middle row of the tube near the surface of the cation resin, soak 1.5-2 hours, drain the column of waste acid.
Valve operation: open the acid inlet pump valve, acid pump pressure reducing valve, acid inlet valve, regulating valve, discharge valve in the valve (where the acid pump pressure reducing valve is to adjust the pressure of acid inlet, open the discharge valve when discharging).    , , and
(3) dynamic regeneration: pump the remaining regeneration solution into the column, the flow rate must be slow, flush the resin l5-30 minutes until the regeneration solution is used up.
Valve operation: open the acid inlet pump valve, acid pump pressure reducing valve, acid inlet valve, regulating valve, outlet valve, middle discharge valve (where the acid pump pressure reducing valve is to adjust the pressure of incoming acid, open the discharge valve when discharging).

6, flushing: flush the resin with primary desalinated water from the lower part of the inlet, discharge from the discharge pipe, the flow rate (about 15m / h) must be uniform, test the ion exchange column with PH test paper in the discharge pipe water, PH value of 5-6, you can stop flushing.
Valve operation: open the water inlet valve, backwash valve and discharge valve, stop flushing open the discharge valve for about l-2 minutes.   

Caution.
When feeding regeneration liquid, be sure not to let the acid exceed the liquid level of the positive resin, otherwise the negative resin will be affected by the acid and fail.   
Key points: In the regeneration process of Yin and Yang resin, the soaking must be sufficient, the regeneration solution must be evenly prepared, and the regeneration material must be clean and free of pollution. After flushing, the concentration of acid and alkali must be neutralized to neutral after mixing.

7, mixed bed mixing approach.

(1), with compressed air (or nitrogen, etc.) mixing steps.

(1) will be added to the column of primary demineralized water, the liquid level is maintained above the resin surface l5-20cm. 
Valve operation: open the water inlet valve and exhaust valve.

② Connect clean, dry oil-free compressed air, from the bottom of the air intake, the upper exhaust valve discharge, control the air pressure at 0.1-1.5MPa, so that the column of resin loose into boiling.
Valve operation: open the lower intake valve or discharge valve (connected to compressed air) and exhaust valve.   

③Close the compressed air and drain the water quickly from the bottom, until the water is drained.

④Repeat the above operation 4-6 times until the mixture is completely uniform to start using.   

(2), mixing steps with vacuum pump.

① Add primary desalinated water to the column, and keep the liquid level above the resin surface l5-20cm.
Valve operation: open the water inlet valve and exhaust valve.

② Connect the upper exhaust valve to the vacuum pump, pump the vacuum from the top, the lower exhaust valve into the air, control the vacuum pressure at 0.15-0.2MPa, so that the resin in the column loose into a boiling state. From the outside, the column of Yin and Yang resin mixed evenly.
Valve operation: open the upper exhaust valve (connected to the vacuum pump) and the lower discharge valve.   

③Shut down the vacuum pump and release water quickly from the bottom, until the water is discharged.   

④Repeat the above operation 4-6 times until it is completely mixed evenly and can start to use again.

Caution.       

① Drain water must be timely to prevent stratification in the process of resin drop.   

② Mixing must be thoroughly and evenly to ensure regeneration quality and water quality.

③ Strict inspection, do not make the compressed air with oil, so as not to contaminate the resin.

8, positive washing: after mixing the negative and positive resin, inject the primary desalinated water from the upper part through the inlet valve and discharge it from the lower discharge valve; flush the resin at a flow rate of l0-15m/h until the effluent is qualified.

9、Normal operation.   

(1) the primary desalination water injected into the exchange column, open the exhaust valve, after filling with water to close the exhaust valve, open the outlet valve, measure the ion exchange column water quality at the outlet valve. Generally in the operation of l5-25 minutes, the water can reach normal, the water can be qualified (to 20 - 40m / h speed) run out of water.
Valve operation: open the water inlet valve, water outlet valve, exhaust valve, fill with water and close the exhaust valve.    Cautions.

① just regenerated ion exchange column needs to be flushed for ten minutes, just flushed when the water quality is poor, need to wait until the water is qualified before it can be put into normal operation.

② ion exchange column into the water must first open the exhaust valve, wait until the column is completely filled with water, and then close it.

③ new column water if not qualified, should immediately stop the water, stop a few hours before running, the water quality will be greatly improved.

Valve Summary List